Turn free multilingual text into a URL-safe slug. Transliterates Latin (all diacritics: é→e, ü→u), Cyrillic and Greek to ASCII; deterministic. Options: separator (default '-'), lowercase (default true), maxLength (cuts on a word boundary), transliterate (default true; false keeps letters of any script as a Unicode slug). Complex scripts (CJK, Arabic, Hebrew) are NOT romanised and are dropped.